The major goal of this program is to analyze the detailed structure of the nucleosome and other closely related constituents of genetic material. These macromolecules are elements in the primary functions of chromatin: transcription and regulation, replication, and DNA packaging. Several biophysical and biochemical techniques will be utilized to study these molecules, with the primary effort consisting of (1) X-ray crytallography of nucleosomes and (2) small-angle neutron scattering on oriented 30 nm chromatin fibers. The main objective will be to determine a medium to high resolution crystallographic structure of the nucleosome core particle. One or more appropriate crystal forms will be obtained by crystallization of nucleosomes reconstituted from purified histones and specific sequence DNA. The structure(s) will then be solved using heavy atom derivative phasing and synchrotron radiation to a resolution of 3 A. Attempts may also be made to crystallize complexes between histone H1 and DNA or core nuclesomes, precisely defined nucleosome multimers, and other related materials for future study. Small-angle neutron scattering on 30 nm chromatin fibers will be carried out using a system developed at Oak Ridge for viscous shear alignment of fibers for solution scattering.